1. Field of the Invention
The present invention relates to an exposure apparatus having a projection optical system for projecting a pattern of a first object onto a photosensitive substrate etc. as a second object, and more particularly to a projection optical system suitably applicable to projection exposure of a pattern for semiconductor or liquid crystal formed on a reticle (mask) as the first object onto the substrate (semiconductor wafer, plate, etc.) as the second object.
2. Related Background Art
As the pasterns of integrated circuits become finer and finer, the resolving power required for the exposure apparatus used in printing of wafer also becomes higher and higher. In addition to the improvement in resolving power, the projection optical systems of the exposure apparatus are required to decrease image stress.
Here, the image stress includes those due to bowing etc. of the printed wafer on the image side of projection optical system and those due to bowing etc. of the reticle with circuit pattern etc. written therein, on the object side of projection optical system, as well as distortion caused by the projection optical system.
With a recent further progress of fineness tendency of transfer patterns, demands to decrease the image stress are also becoming harder.
Then, in order to decrease effects of the wafer bowing on the image stress, the conventional technology has employed the so-called image-side telecentric optical system that located the exit pupil position at a farther point on the image side of projection optical system.
On the other hand, the image stress due to the bowing of reticle can also be reduced by employing a so-called object-side telecentric optical system that locates the entrance pupil position of projection optical system at a farther point from the object plane, and there are suggestions to locate the entrance pupil position of projection optical system at a relatively far position from the object plane as described. Examples of those suggestions are described for example in Japanese Laid-open Patent Applications No. 63-118115 and No. 5-173065 and U.S. Pat. No. 5,260,832.